LP#1705731: background batch MARC edits now report status less verbosely

LP#1705731: background batch MARC edits now report status less verbosely

Rather than repeatedly inserting and fetching potentially
very large arrays of per-record status statements from the
anon cache, batch MARC edits that are run in the background
now report counts.

This patch changes how open-ils.cat.container.template_overlay.background
populates the anonymous cache; note that streaming status updates
if calling open-ils.cat.container.template_overlay instead are
*not* changed.

To test
-------
[1] Set up a MARC Batch Edit run using a reasonably large bucket
    as a source records.
[2] Verify that progress is reported correctly during the run.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>